[PATCH v2 0/2] kunit: fail tests on UBSAN errors

[Daniel Latypov]

v1 by Uriel is here: [1].
Since it's been a while, I've dropped the Reviewed-By's.

It depended on commit 83c4e7a0363b ("KUnit: KASAN Integration") which
hadn't been merged yet, so that caused some kerfuffle with applying them
previously and the series was reverted.

This revives the series but makes the kunit_fail_current_test() function
take a format string and logs the file and line number of the failing
code, addressing Alan Maguire's comments on the previous version.

As a result, the patch that makes UBSAN errors was tweaked slightly to
include an error message.

[1] https://lore.kernel.org/linux-kselftest/20200806174326.35775...@gmail.com/

Uriel Guajardo (2):
kunit: support failure from dynamic analysis tools
kunit: ubsan integration

include/kunit/test-bug.h | 30 ++++++++++++++++++++++++++++++
lib/kunit/test.c | 36 ++++++++++++++++++++++++++++++++----
lib/ubsan.c | 3 +++
3 files changed, 65 insertions(+), 4 deletions(-)
create mode 100644 include/kunit/test-bug.h


base-commit: 1e0d27fce010b0a4a9e595506b6ede75934c31be
--
2.30.0.478.g8a0d178c01-goog

[Daniel Latypov]

From: Uriel Guajardo <urielg...@google.com>

Add a kunit_fail_current_test() function to fail the currently running
test, if any, with an error message.

This is largely intended for dynamic analysis tools like UBSAN and for
fakes.
E.g. say I had a fake ops struct for testing and I wanted my `free`
function to complain if it was called with an invalid argument, or
caught a double-free. Most return void and have no normal means of
signalling failure (e.g. super_operations, iommu_ops, etc.).

Key points:
* Always update current->kunit_test so anyone can use it.
* commit 83c4e7a0363b ("KUnit: KASAN Integration") only updated it for
CONFIG_KASAN=y

* Create a new header <kunit/test-bug.h> so non-test code doesn't have
to include all of <kunit/test.h> (e.g. lib/ubsan.c)

* Forward the file and line number to make it easier to track down
failures

* Declare it as a function for nice __printf() warnings about mismatched
format strings even when KUnit is not enabled.

Example output from kunit_fail_current_test("message"):
[15:19:34] [FAILED] example_simple_test
[15:19:34] # example_simple_test: initializing
[15:19:34] # example_simple_test: lib/kunit/kunit-example-test.c:24: message
[15:19:34] not ok 1 - example_simple_test

Co-developed-by: Daniel Latypov <dlat...@google.com>
Signed-off-by: Uriel Guajardo <urielg...@google.com>
Signed-off-by: Daniel Latypov <dlat...@google.com>
---

include/kunit/test-bug.h | 30 ++++++++++++++++++++++++++++++
lib/kunit/test.c | 36 ++++++++++++++++++++++++++++++++----

2 files changed, 62 insertions(+), 4 deletions(-)
create mode 100644 include/kunit/test-bug.h

diff --git a/include/kunit/test-bug.h b/include/kunit/test-bug.h
new file mode 100644
index 000000000000..4963ed52c2df
--- /dev/null
+++ b/include/kunit/test-bug.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * KUnit API allowing dynamic analysis tools to interact with KUnit tests
+ *
+ * Copyright (C) 2020, Google LLC.
+ * Author: Uriel Guajardo <urielg...@google.com>
+ */
+
+#ifndef _KUNIT_TEST_BUG_H
+#define _KUNIT_TEST_BUG_H
+
+#define kunit_fail_current_test(fmt, ...) \
+ _kunit_fail_current_test(__FILE__, __LINE__, fmt, ##__VA_ARGS__)
+
+#if IS_ENABLED(CONFIG_KUNIT)
+
+extern __printf(3, 4) void _kunit_fail_current_test(const char *file, int line,
+ const char *fmt, ...);
+
+#else
+
+static __printf(3, 4) void _kunit_fail_current_test(const char *file, int line,
+ const char *fmt, ...)
+{
+}
+
+#endif
+
+
+#endif /* _KUNIT_TEST_BUG_H */
diff --git a/lib/kunit/test.c b/lib/kunit/test.c
index ec9494e914ef..7b16aae0ccae 100644
--- a/lib/kunit/test.c
+++ b/lib/kunit/test.c
@@ -7,6 +7,7 @@
*/

#include <kunit/test.h>
+#include <kunit/test-bug.h>
#include <linux/kernel.h>
#include <linux/kref.h>
#include <linux/sched/debug.h>
@@ -16,6 +17,37 @@
#include "string-stream.h"
#include "try-catch-impl.h"

+/*
+ * Fail the current test and print an error message to the log.
+ */
+void _kunit_fail_current_test(const char *file, int line, const char *fmt, ...)
+{
+ va_list args;
+ int len;
+ char *buffer;
+
+ if (!current->kunit_test)
+ return;
+
+ kunit_set_failure(current->kunit_test);
+
+ /* kunit_err() only accepts literals, so evaluate the args first. */
+ va_start(args, fmt);
+ len = vsnprintf(NULL, 0, fmt, args) + 1;
+ va_end(args);
+
+ buffer = kunit_kmalloc(current->kunit_test, len, GFP_KERNEL);
+ if (!buffer)
+ return;
+
+ va_start(args, fmt);
+ vsnprintf(buffer, len, fmt, args);
+ va_end(args);
+
+ kunit_err(current->kunit_test, "%s:%d: %s", file, line, buffer);
+ kunit_kfree(current->kunit_test, buffer);
+}
+
/*
* Append formatted message to log, size of which is limited to
* KUNIT_LOG_SIZE bytes (including null terminating byte).
@@ -273,9 +305,7 @@ static void kunit_try_run_case(void *data)
struct kunit_suite *suite = ctx->suite;
struct kunit_case *test_case = ctx->test_case;

-#if (IS_ENABLED(CONFIG_KASAN) && IS_ENABLED(CONFIG_KUNIT))
current->kunit_test = test;
-#endif /* IS_ENABLED(CONFIG_KASAN) && IS_ENABLED(CONFIG_KUNIT) */

/*
* kunit_run_case_internal may encounter a fatal error; if it does,
@@ -624,9 +654,7 @@ void kunit_cleanup(struct kunit *test)
spin_unlock(&test->lock);
kunit_remove_resource(test, res);
}
-#if (IS_ENABLED(CONFIG_KASAN) && IS_ENABLED(CONFIG_KUNIT))
current->kunit_test = NULL;
-#endif /* IS_ENABLED(CONFIG_KASAN) && IS_ENABLED(CONFIG_KUNIT)*/
}
EXPORT_SYMBOL_GPL(kunit_cleanup);

--
2.30.0.478.g8a0d178c01-goog

[Daniel Latypov]

From: Uriel Guajardo <urielg...@google.com>

Integrates UBSAN into the KUnit testing framework. It fails KUnit tests
whenever it reports undefined behavior.

When CONFIG_KUNIT=n, nothing is printed or even formatted, so this has
no behavioral impact outside of tests.

kunit_fail_current_test() effectively does a pr_err() as well, so
there's some slight duplication, but it also ensures an error is
recorded in the debugfs entry for the running KUnit test.

Print a shorter version of the message to make it less spammy.

Co-developed-by: Daniel Latypov <dlat...@google.com>
Signed-off-by: Uriel Guajardo <urielg...@google.com>
Signed-off-by: Daniel Latypov <dlat...@google.com>
---

lib/ubsan.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/lib/ubsan.c b/lib/ubsan.c
index bec38c64d6a6..1ec7d6f1fe63 100644
--- a/lib/ubsan.c
+++ b/lib/ubsan.c
@@ -14,6 +14,7 @@
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/uaccess.h>
+#include <kunit/test-bug.h>

#include "ubsan.h"

@@ -141,6 +142,8 @@ static void ubsan_prologue(struct source_location *loc, const char *reason)
"========================================\n");
pr_err("UBSAN: %s in %s:%d:%d\n", reason, loc->file_name,
loc->line & LINE_MASK, loc->column & COLUMN_MASK);
+
+ kunit_fail_current_test("%s in %s", reason, loc->file_name);
}

static void ubsan_epilogue(void)
--
2.30.0.478.g8a0d178c01-goog

[Alan Maguire]

On Fri, 5 Feb 2021, Daniel Latypov wrote:

> From: Uriel Guajardo <urielg...@google.com>
>
> Add a kunit_fail_current_test() function to fail the currently running
> test, if any, with an error message.
>
> This is largely intended for dynamic analysis tools like UBSAN and for
> fakes.
> E.g. say I had a fake ops struct for testing and I wanted my `free`
> function to complain if it was called with an invalid argument, or
> caught a double-free. Most return void and have no normal means of
> signalling failure (e.g. super_operations, iommu_ops, etc.).
>
> Key points:
> * Always update current->kunit_test so anyone can use it.
> * commit 83c4e7a0363b ("KUnit: KASAN Integration") only updated it for
> CONFIG_KASAN=y
>
> * Create a new header <kunit/test-bug.h> so non-test code doesn't have
> to include all of <kunit/test.h> (e.g. lib/ubsan.c)
>
> * Forward the file and line number to make it easier to track down
> failures
>

Thanks for doing this!

> * Declare it as a function for nice __printf() warnings about mismatched
> format strings even when KUnit is not enabled.
>

One thing I _think_ this assumes is that KUnit is builtin;
don't we need an

EXPORT_SYMBOL_GPL(_kunit_fail_current_test);

?

Without it, if an analysis tool (or indeed if KUnit) is built
as a module, it won't be possible to use this functionality.

> Example output from kunit_fail_current_test("message"):
> [15:19:34] [FAILED] example_simple_test
> [15:19:34] # example_simple_test: initializing
> [15:19:34] # example_simple_test: lib/kunit/kunit-example-test.c:24: message
> [15:19:34] not ok 1 - example_simple_test
>
> Co-developed-by: Daniel Latypov <dlat...@google.com>
> Signed-off-by: Uriel Guajardo <urielg...@google.com>
> Signed-off-by: Daniel Latypov <dlat...@google.com>
> ---
> include/kunit/test-bug.h | 30 ++++++++++++++++++++++++++++++
> lib/kunit/test.c | 36 ++++++++++++++++++++++++++++++++----
> 2 files changed, 62 insertions(+), 4 deletions(-)
> create mode 100644 include/kunit/test-bug.h
>
> diff --git a/include/kunit/test-bug.h b/include/kunit/test-bug.h
> new file mode 100644
> index 000000000000..4963ed52c2df
> --- /dev/null
> +++ b/include/kunit/test-bug.h
> @@ -0,0 +1,30 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * KUnit API allowing dynamic analysis tools to interact with KUnit tests
> + *
> + * Copyright (C) 2020, Google LLC.

nit; might want to update copyright year.

[Daniel Latypov]

On Tue, Feb 9, 2021 at 9:26 AM Alan Maguire <alan.m...@oracle.com> wrote:
>
> On Fri, 5 Feb 2021, Daniel Latypov wrote:
>
> > From: Uriel Guajardo <urielg...@google.com>
> >
> > Add a kunit_fail_current_test() function to fail the currently running
> > test, if any, with an error message.
> >
> > This is largely intended for dynamic analysis tools like UBSAN and for
> > fakes.
> > E.g. say I had a fake ops struct for testing and I wanted my `free`
> > function to complain if it was called with an invalid argument, or
> > caught a double-free. Most return void and have no normal means of
> > signalling failure (e.g. super_operations, iommu_ops, etc.).
> >
> > Key points:
> > * Always update current->kunit_test so anyone can use it.
> > * commit 83c4e7a0363b ("KUnit: KASAN Integration") only updated it for
> > CONFIG_KASAN=y
> >
> > * Create a new header <kunit/test-bug.h> so non-test code doesn't have
> > to include all of <kunit/test.h> (e.g. lib/ubsan.c)
> >
> > * Forward the file and line number to make it easier to track down
> > failures
> >
>
> Thanks for doing this!
>
> > * Declare it as a function for nice __printf() warnings about mismatched
> > format strings even when KUnit is not enabled.
> >
>
> One thing I _think_ this assumes is that KUnit is builtin;
> don't we need an

Ah, you're correct.
Also going to rename it to have two _ to match other functions used in
macros like __kunit_test_suites_init.

I had been having some recent issues with getting QEMU to work on my
machine so I hadn't tested it before.
Somehow I've finally fixed it and can now say that it works w/
CONFIG_KUNIT=m after making the change

# modprobe kunit
# modprobe kunit-example-test
[ 27.689840] # Subtest: example
[ 27.689994] 1..1
[ 27.692337] # example_simple_test: initializing
[ 27.692862] # example_simple_test:
lib/kunit/kunit-example-test.c:31: example failure message: 42
[ 27.693158] not ok 1 - example_simple_test
[ 27.693654] not ok 1 - example

[Alan Maguire]

Great! If you're sending out an updated version with these
changes, feel free to add

Reviewed-by: Alan Maguire <alan.m...@oracle.com>

[Daniel Latypov]

v1 by Uriel is here: [1].
Since it's been a while, I've dropped the Reviewed-By's.

It depended on commit 83c4e7a0363b ("KUnit: KASAN Integration") which
hadn't been merged yet, so that caused some kerfuffle with applying them
previously and the series was reverted.

This revives the series but makes the kunit_fail_current_test() function
take a format string and logs the file and line number of the failing
code, addressing Alan Maguire's comments on the previous version.

As a result, the patch that makes UBSAN errors was tweaked slightly to
include an error message.

v2 -> v3:
Fix kunit_fail_current_test() so it works w/ CONFIG_KUNIT=m
s/_/__ on the helper func to match others in test.c

[1] https://lore.kernel.org/linux-kselftest/20200806174326.35775...@gmail.com/

Uriel Guajardo (2):
kunit: support failure from dynamic analysis tools
kunit: ubsan integration

include/kunit/test-bug.h | 30 ++++++++++++++++++++++++++++++

lib/kunit/test.c | 37 +++++++++++++++++++++++++++++++++----
lib/ubsan.c | 3 +++
3 files changed, 66 insertions(+), 4 deletions(-)
create mode 100644 include/kunit/test-bug.h


base-commit: 1e0d27fce010b0a4a9e595506b6ede75934c31be
--
2.30.0.478.g8a0d178c01-goog

[Daniel Latypov]

From: Uriel Guajardo <urielg...@google.com>

Add a kunit_fail_current_test() function to fail the currently running
test, if any, with an error message.

This is largely intended for dynamic analysis tools like UBSAN and for
fakes.
E.g. say I had a fake ops struct for testing and I wanted my `free`
function to complain if it was called with an invalid argument, or
caught a double-free. Most return void and have no normal means of
signalling failure (e.g. super_operations, iommu_ops, etc.).

Key points:
* Always update current->kunit_test so anyone can use it.
* commit 83c4e7a0363b ("KUnit: KASAN Integration") only updated it for
CONFIG_KASAN=y

* Create a new header <kunit/test-bug.h> so non-test code doesn't have
to include all of <kunit/test.h> (e.g. lib/ubsan.c)

* Forward the file and line number to make it easier to track down
failures

* Declare the helper function for nice __printf() warnings about mismatched

format strings even when KUnit is not enabled.

Example output from kunit_fail_current_test("message"):
[15:19:34] [FAILED] example_simple_test
[15:19:34] # example_simple_test: initializing
[15:19:34] # example_simple_test: lib/kunit/kunit-example-test.c:24: message
[15:19:34] not ok 1 - example_simple_test

Co-developed-by: Daniel Latypov <dlat...@google.com>
Signed-off-by: Uriel Guajardo <urielg...@google.com>
Signed-off-by: Daniel Latypov <dlat...@google.com>
---

include/kunit/test-bug.h | 30 ++++++++++++++++++++++++++++++
lib/kunit/test.c | 37 +++++++++++++++++++++++++++++++++----

2 files changed, 63 insertions(+), 4 deletions(-)
create mode 100644 include/kunit/test-bug.h

diff --git a/include/kunit/test-bug.h b/include/kunit/test-bug.h
new file mode 100644

index 000000000000..18b1034ec43a

--- /dev/null
+++ b/include/kunit/test-bug.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * KUnit API allowing dynamic analysis tools to interact with KUnit tests
+ *
+ * Copyright (C) 2020, Google LLC.

+ * Author: Uriel Guajardo <urielg...@google.com>
+ */
+
+#ifndef _KUNIT_TEST_BUG_H
+#define _KUNIT_TEST_BUG_H
+
+#define kunit_fail_current_test(fmt, ...) \

+ __kunit_fail_current_test(__FILE__, __LINE__, fmt, ##__VA_ARGS__)
+
+#if IS_ENABLED(CONFIG_KUNIT)
+
+extern __printf(3, 4) void __kunit_fail_current_test(const char *file, int line,

+ const char *fmt, ...);
+
+#else
+

+static __printf(3, 4) void __kunit_fail_current_test(const char *file, int line,

+ const char *fmt, ...)
+{
+}
+
+#endif
+
+
+#endif /* _KUNIT_TEST_BUG_H */
diff --git a/lib/kunit/test.c b/lib/kunit/test.c

index ec9494e914ef..5794059505cf 100644

--- a/lib/kunit/test.c
+++ b/lib/kunit/test.c
@@ -7,6 +7,7 @@
*/

#include <kunit/test.h>
+#include <kunit/test-bug.h>
#include <linux/kernel.h>
#include <linux/kref.h>
#include <linux/sched/debug.h>

@@ -16,6 +17,38 @@

#include "string-stream.h"
#include "try-catch-impl.h"

+/*
+ * Fail the current test and print an error message to the log.
+ */

+void __kunit_fail_current_test(const char *file, int line, const char *fmt, ...)

+EXPORT_SYMBOL_GPL(__kunit_fail_current_test);

+
/*
* Append formatted message to log, size of which is limited to
* KUNIT_LOG_SIZE bytes (including null terminating byte).

@@ -273,9 +306,7 @@ static void kunit_try_run_case(void *data)

struct kunit_suite *suite = ctx->suite;
struct kunit_case *test_case = ctx->test_case;

-#if (IS_ENABLED(CONFIG_KASAN) && IS_ENABLED(CONFIG_KUNIT))
current->kunit_test = test;
-#endif /* IS_ENABLED(CONFIG_KASAN) && IS_ENABLED(CONFIG_KUNIT) */

/*
* kunit_run_case_internal may encounter a fatal error; if it does,

@@ -624,9 +655,7 @@ void kunit_cleanup(struct kunit *test)

[Daniel Latypov]

From: Uriel Guajardo <urielg...@google.com>

Integrates UBSAN into the KUnit testing framework. It fails KUnit tests
whenever it reports undefined behavior.

When CONFIG_KUNIT=n, nothing is printed or even formatted, so this has
no behavioral impact outside of tests.

kunit_fail_current_test() effectively does a pr_err() as well, so
there's some slight duplication, but it also ensures an error is
recorded in the debugfs entry for the running KUnit test.

Print a shorter version of the message to make it less spammy.

Co-developed-by: Daniel Latypov <dlat...@google.com>
Signed-off-by: Uriel Guajardo <urielg...@google.com>
Signed-off-by: Daniel Latypov <dlat...@google.com>
---

[Daniel Latypov]

Oops, there was a race in sending v3 and seeing this in my inbox.

If you could reply to the v3 that'd be great. I've already amended the
commit locally.
Thanks!

[Alan Maguire]

On Tue, 9 Feb 2021, Daniel Latypov wrote:

> v1 by Uriel is here: [1].
> Since it's been a while, I've dropped the Reviewed-By's.
>
> It depended on commit 83c4e7a0363b ("KUnit: KASAN Integration") which
> hadn't been merged yet, so that caused some kerfuffle with applying them
> previously and the series was reverted.
>
> This revives the series but makes the kunit_fail_current_test() function
> take a format string and logs the file and line number of the failing
> code, addressing Alan Maguire's comments on the previous version.
>
> As a result, the patch that makes UBSAN errors was tweaked slightly to
> include an error message.
>
> v2 -> v3:
> Fix kunit_fail_current_test() so it works w/ CONFIG_KUNIT=m
> s/_/__ on the helper func to match others in test.c
>
> [1] https://lore.kernel.org/linux-kselftest/20200806174326.35775...@gmail.com/
>

For the series:

Reviewed-by: Alan Maguire <alan.m...@oracle.com>

Thanks!

[kernel test robot]

Hi Daniel,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v5.11-rc7 next-20210125]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url: https://github.com/0day-ci/linux/commits/Daniel-Latypov/kunit-support-failure-from-dynamic-analysis-tools/20210210-074913
base: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git e0756cfc7d7cd08c98a53b6009c091a3f6a50be6
config: m68k-allmodconfig (attached as .config)
compiler: m68k-linux-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# https://github.com/0day-ci/linux/commit/e3ddf9fb46a603f7e8bf3918cb707a0da9681a17
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Daniel-Latypov/kunit-support-failure-from-dynamic-analysis-tools/20210210-074913
git checkout e3ddf9fb46a603f7e8bf3918cb707a0da9681a17
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=m68k

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <l...@intel.com>

All errors (new ones prefixed by >>):

m68k-linux-ld: lib/ubsan.o: in function `ubsan_prologue':
>> ubsan.c:(.text.unlikely+0x142): undefined reference to `__kunit_fail_current_test'

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuil...@lists.01.org

[kernel test robot]

Hi Daniel,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v5.11-rc7 next-20210125]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url: https://github.com/0day-ci/linux/commits/Daniel-Latypov/kunit-support-failure-from-dynamic-analysis-tools/20210210-074913
base: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git e0756cfc7d7cd08c98a53b6009c091a3f6a50be6

config: mips-allmodconfig (attached as .config)
compiler: mips-linux-gcc (GCC) 9.3.0

reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# https://github.com/0day-ci/linux/commit/e3ddf9fb46a603f7e8bf3918cb707a0da9681a17
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Daniel-Latypov/kunit-support-failure-from-dynamic-analysis-tools/20210210-074913
git checkout e3ddf9fb46a603f7e8bf3918cb707a0da9681a17
# save the attached .config to linux build tree

COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=mips

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <l...@intel.com>

All errors (new ones prefixed by >>):

mips-linux-ld: lib/ubsan.o: in function `ubsan_prologue':
>> ubsan.c:(.text.unlikely.ubsan_prologue+0x80): undefined reference to `__kunit_fail_current_test'

[David Gow]

As the kernel test robot has pointed out on the second patch, this
probably should be IS_BUILTIN(), otherwise this won't build if KUnit
is a module, and the code calling it isn't.

This does mean that things like UBSAN integration won't work if KUnit
is a module, which is a shame.

(It's worth noting that the KASAN integration worked around this by
only calling inline functions, which would therefore be built-in even
if the rest of KUnit was built as a module. I don't think it's quite
as convenient to do that here, though.)

[Alan Maguire]

Right, static inline'ing __kunit_fail_current_test() seems problematic
because it calls other exported functions; more below....

currently kunit_set_failure() is static, but it could be inlined I
suspect.

> > + /* kunit_err() only accepts literals, so evaluate the args first. */
> > + va_start(args, fmt);
> > + len = vsnprintf(NULL, 0, fmt, args) + 1;
> > + va_end(args);
> > +
> > + buffer = kunit_kmalloc(current->kunit_test, len, GFP_KERNEL);

kunit_kmalloc()/kunit_kfree() are exported also, but we could probably
dodge allocation with a static buffer. In fact since we end up
using an on-stack buffer for logging in kunit_log_append(), it might make
sense to #define __kunit_fail_current_test() instead, i.e.

#define __kunit_fail_current_test(file, line, fmt, ...) \
do { \
kunit_set_failure(current->kunit_test); \
kunit_err(current->kunit_test, "%s:%d: " fmt, \
##__VA_ARGS__); \
} while (0)

> > + if (!buffer)
> > + return;
> > +
> > + va_start(args, fmt);
> > + vsnprintf(buffer, len, fmt, args);
> > + va_end(args);
> > +
> > + kunit_err(current->kunit_test, "%s:%d: %s", file, line, buffer);

To get kunit_err() to work, we'd need to "static inline"
kunit_log_append(). It's not a trivial function, but on the plus
side it doesn't call any other exported kunit functions AFAICT.

So while any of the above suggestions aren't intended to block
Daniel's work, does the above seem reasonable for a follow-up
series to get UBSAN working with module-based KUnit? Thanks!

Alan

[Daniel Latypov]

Ah, right there's those as well.

I originally had it on the stack, but the fact we use an on-stack
buffer is why I switched over.

I originally had it as a macro as you do now but liked the __printf()
annotation to be closer* to the user's code and now down through
several layers of macros (kunit_fail_current_test => kunit_err =>
kunit_printk => kunit_log => printk).
And then having it on the stack and then calling into
kunit_log_append() would (naively) use up 2 *KUNIT_LOG_SIZE stack
space.

So only a minor concern, and so I like the simpler def using a macro
given the messiness.
(But we'd give up the __printf checking when compiling w/o KUnit,
which is a bit sad)

*E.g. if one misuses kunit_err(), we get this message which is
understandable, but a bit more noisy than I'd prefer.
../include/linux/kern_levels.h:5:18: warning: format ‘%d’ expects
argument of type ‘int’, but argument 3 has type ‘char *’ [-Wformat=]
5 | #define KERN_SOH "\001" /* ASCII Start Of Header */
| ^~~~~~
../include/kunit/test.h:621:10: note: in definition of macro ‘kunit_log’
621 | printk(lvl fmt, ##__VA_ARGS__); \
| ^~~
../include/kunit/test.h:662:2: note: in expansion of macro ‘kunit_printk’
662 | kunit_printk(KERN_ERR, test, fmt, ##__VA_ARGS__)
| ^~~~~~~~~~~~
../include/linux/kern_levels.h:11:18: note: in expansion of macro ‘KERN_SOH’
11 | #define KERN_ERR KERN_SOH "3" /* error conditions */
| ^~~~~~~~
../include/kunit/test.h:662:15: note: in expansion of macro ‘KERN_ERR’
662 | kunit_printk(KERN_ERR, test, fmt, ##__VA_ARGS__)
| ^~~~~~~~
../lib/kunit/kunit-example-test.c:30:2: note: in expansion of macro ‘kunit_err’
30 | kunit_err(test, "invalid format string: %d", "hi");
| ^~~~~~~~~

> sense to #define __kunit_fail_current_test() instead, i.e.
>
> #define __kunit_fail_current_test(file, line, fmt, ...) \
> do { \
> kunit_set_failure(current->kunit_test); \
> kunit_err(current->kunit_test, "%s:%d: " fmt, \
> ##__VA_ARGS__); \
> } while (0)
>
> > > + if (!buffer)
> > > + return;
> > > +
> > > + va_start(args, fmt);
> > > + vsnprintf(buffer, len, fmt, args);
> > > + va_end(args);
> > > +
> > > + kunit_err(current->kunit_test, "%s:%d: %s", file, line, buffer);
>
> To get kunit_err() to work, we'd need to "static inline"
> kunit_log_append(). It's not a trivial function, but on the plus
> side it doesn't call any other exported kunit functions AFAICT.
>
> So while any of the above suggestions aren't intended to block
> Daniel's work, does the above seem reasonable for a follow-up
> series to get UBSAN working with module-based KUnit? Thanks!

Ack, so sounds like we'd want to go ahead with making it only work w/
CONFIG_KUNIT=y?

I can simplify it down into a macro since the __printf() bit isn't too
big of a deal.
And then it'd let us only depend on kunit_log_append(), making it
easier to get CONFIG_KUNIT=m working.

Thanks both for digging into this!
I saw KTR's email and was dreading having to dig into what the
smallest needed change would be.

>
> Alan

[Brendan Higgins]

I also think this is probably only useful when KUnit is built in.
Although it would be certainly neat to be able to support utilizing
`current->kunit_test` after the fact when KUnit is built as a module,
the problem is that `kunit_test` is only a member of the task_struct
when KUnit is enabled anyway:

https://elixir.bootlin.com/linux/v5.10.15/source/include/linux/sched.h#L1234

I think that making `kunit_test` always present in task_struct is
undesirable for many users, and so you then have to be sure that your
kernel you want to load the KUnit module into was built with
CONFIG_KUNIT=m.

Overall, I think it is safer and easier to just require KUnit to be
built in if you want to use `current->kunit_test`. In any case, that
does not take away the ability to use KUnit test modules with it, just
not KUnit itself as a module (CONFIG_KUNIT=y is compatible with tests
built as modules).

[Daniel Latypov]

Good point, will change to IS_BUILTIN(), in that case.

>
> > I can simplify it down into a macro since the __printf() bit isn't too
> > big of a deal.
> > And then it'd let us only depend on kunit_log_append(), making it
> > easier to get CONFIG_KUNIT=m working.

Ugh, actually, I'll have to walk back making it a macro for now...
The goal had been that <kunit/test-bug.h> wouldn't pull in kunit code.

We can forward declare kunit_set_failure(), but not kunit_err(), which
is a macro.
So to make a static inline or macro version of
kunit_fail_current_test() requires pulling in <kunit/test.h>

> >
> > Thanks both for digging into this!
> > I saw KTR's email and was dreading having to dig into what the
> > smallest needed change would be.
> >
> > >
> > > Alan
>

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